Trachionus acarinatus Cui & van Achterberg

Cui, Qian, van Achterberg, Cornelis, Tan, Jiang-Li & Chen, Xue-Xin, 2015, The genus Trachionus Haliday, 1833 (Hymenoptera, Braconidae, Alysiinae) new for China, with description of four new species, ZooKeys 512, pp. 19-37: 21-25

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Trachionus acarinatus Cui & van Achterberg

sp. n.

Taxon classification Animalia Hymenoptera Braconidae

Trachionus acarinatus Cui & van Achterberg   sp. n. Figs 1, 2-10, 46

Type material.

Holotype, ♂ (NWUX), "NW. China: Shaanxi, Pingheliang, Ningshan, c. 2000 m,, 33°48'N 108°50'E, Jiangli Tan, NWUX". Paratype: 1 ♂ (ZJUH), topotypic and same data.


Scutellum largely smooth and nearly flat; mandible without fourth ventral tooth (Fig. 46); metanotal spine long, its highest point reaching level of tips of setae of scutellum (Fig. 10); propleuron without distinct transverse carina subposteriorly; precoxal sulcus and notauli medium-sized; propodeum gradually lowered posteriorly in lateral view and carina distinctly protruding postero-laterally (Fig. 4); second and third tergites regularly and rather finely striate, with about 60 striae and moderately shiny (Fig. 5). Similar to Trachionus hians   (Nees, 1816), but that species has a strong transverse carina at the propleuron subposteriorly (absent or slightly developed in Trachionus acarinatus   ); precoxal sulcus and posterior part of notauli wide (medium-sized) and metanotal spine hardly protruding above level of scutellum (protruding far above level of scutellum).


Holotype, male; body length 3.4 mm, forewing length 3.3 mm.

Head. Width of head twice its median length; head dorsally smooth, strongly shiny and largely sparsely setose; antenna with 33 segments, 0.95 × as long as forewing, third segment 1.6 × as long as fourth segment, length of third, fourth and penultimate segments 2.6 ×, 1.7 × and 1.6 × their width, respectively; frons slightly depressed behind antennal sockets and smooth; eye in dorsal view 1.3 × as long as temple; temple in dorsal view directly rounded, smooth and near eye sparsely setose; OOL: diameter of ocellus: POL= 3:1:2; face weakly convex, with distinctly longitudinal carina and down ward pointing setae laterally, largely matt and punctulate; clypeus transverse, with sparse fine punctures and convex; eye glabrous; mandible nearly touching eye, length of malar space 0.1 × basal width of mandible; mandible 1.4 × as long as its maximum width, largely punctate-rugose medially; mandible weakly widened apically, with long and acute triangular middle tooth, and two wide lateral lobes (Fig. 46); maxillary palp 0.9 × height of head.

Mesosoma. Length of mesosoma 1.5 × its height; pronotum laterally mainly smooth except for sparse punctures and rugose posteriorly; propleuron without transverse carina subposteriorly, but slightly developed on left side; epicnemial area largely punctate; precoxal sulcus complete, moderately wide and distinctly crenulate; sternaulus absent; remainder of mesopleuron mostly smooth, dorsally punctate; postpectal carina medially not differentiated from mesosternal rugosity; episternal scrobe large; pleural sulcus finely crenulate dorsally and wider ventrally; mesosternal sulcus medium-sized and moderately crenulate, posteriorly rugose; metapleuron coarsely punctate-reticulate, but dorsally largely smooth; median groove of mesoscutum and notauli complete, narrow and finely crenulate, near posterior end punctate-crenulate; lateral lobes of mesoscutum mostly smooth, shiny, anterior half of middle lobe and area near notauli setose; scutellar sulcus deep and with 2 longitudinal carinae, 0.3 × as long as scutellum; scutellum largely smooth, with few punctures and nearly flat; metanotal spine protruding far above level of scutellum; costulae and double median carina of propodeum distinctly developed but irregular, gradually lowered posteriorly and postero-laterally with protruding carinae; surface of propodeum partly smooth, medially with transverse band of coarse punctate-rugose.

Wings. Pterostigma elliptical; marginal cell of forewing distinctly elongate; vein r issued just before middle of pterostigma (Fig. 2); r:2-SR:3-SR+SR1 = 11:17:69; SR1 curved; 1-CU1:2-CU1 = 1:20; CU1b present; m-cu slightly antefurcal; 1-CU1 hardly widened. Hind wing: M+CU:1-M:1r-m = 28:13:12; cu-a straight; m-cu slightly impressed.

Legs. Hind coxa largely smooth and with long setae; tarsal claws medium-sized (Fig. 9); length of femur, tibia and basitarsus of hind leg 3.9, 9.1 and 5.0 × their width, respectively; all femora widened.

Metasoma. Length of first tergite 1.2 × its apical width, its surface longitudinally coarsely striate, with dorsal carinae converging medially and united in distinct median carina (Fig. 5); second tergite moderately striate, laterally finely striate; third metasomal tergite nearly entirely finely striate, moderately shiny, sparsely setose; combined length of second and third metasomal tergites 0.7 × total length of metasoma (Fig. 6); striae of third tergite with distinct shiny interspaces.

Colour. Black (including mandible); palpi and legs yellow but tarsi and base of hind coxa darkened; tegulae, pterostigma and forewing veins dark brown; hind wing veins pale brown; forewing membrane slightly infuscate, hind wing nearly pellucid.


Forewing length 3.2-3.3 mm, body length 3.3-3.4 mm; antenna with 33 (2 ♂) segments; subposterior transverse carina of propleuron absent or slightly developed; propodeum largely smooth anteriorly or distinctly punctate; paratype has sculpture of metasoma somewhat reduced medio-dorsally.


China (Shaanxi).


The name is derived from “a” (Greek for "not, without") and “carina” (Latin for “ridge”) because of the lacking subposterior transverse carina of the propleuron.